Hello,
A mobile app is still not planned. An app which would offer the equivalent functionalities as the Numista website would require a lot of effort for development and maintenance. Any new feature would have to be developed three times (website, iOS, Android). This is not possible for a team like Numista, even with the new developer joining in. I prefer we spend our time improving the website, while making sure the experience of browsing it from a mobile device is good.